Tweaking font size for pdf conversion

I usually save my web clips as markdown, then convert them to pdf if I need to import them in zotero. I usually do it in iaWriter whose conversion is very clean. Devonthink has its built-in conversion tool, which is very convenient, but the font size in the produced pdf is too small for me to read on screen. Is there a way to increase font size during pdf conversion? (Even a way to chage it from serif to non-serif would be useful).

Markdown rendering uses the rich text font specified in Preferences > Editing (as long as a custom stylesheet isn’t used).

Thanks a lot!